The present invention relates to a printing medium winding apparatus for winding a printing medium such as a printing paper sheet having predetermined dimensions around an outer peripheral surface of a rotating drum, while holding the printing medium on the outer peripheral surface of the drum so that a trailing end portion of the printing medium may not float over the outer peripheral surface of the rotating drum, as well as to an ink-jet printer having such a printing medium winding apparatus.
When a printing medium is wound around an outer peripheral surface of a drum, a trailing end portion of the printing medium may often float over the outer peripheral surface of the drum due to a resilient restoration force by which the printing medium curved on the outer peripheral surface of the drum tends to restore to its original flat shape.
If the rotating drum accompanied with the printing medium winding apparatus is used in, for example, an image forming apparatus including a copying apparatus or a printing apparatus and the trailing end portion of the printing medium wound around the outer peripheral surface of the rotating drum floats over the outer peripheral surface of the rotating drum, an image including characters, numerals, symbols, etc., which is to be recorded on the printing medium in the image forming apparatus, may become unclear near the trailing end of the printing medium. In addition, the floating trailing end portion of the printing medium may abut against, or may be caught by, other various members disposed near the outer peripheral surface of the rotating drum. Consequently, the recording apparatus may fail.
Jpn. Pat. Appl. KOKAI Publication No. 54-38813 and Jpn. Pat. Appl. KOKOKU Publication No. 55-13912, for example, already disclose printing medium winding apparatuses capable of preventing a trailing end portion of a printing medium from floating over the outer peripheral surface of the drum. In particular, the above-mentioned KOKAI Publication No. 54-38813 describes that this type of printing medium winding apparatus is used in an ink-jet printer.
In the printing medium winding apparatus described in KOKAI Publication No. 54-38813, a first groove extending in a longitudinal direction of the drum is provided at a predetermined position on the outer peripheral surface of the drum. A printing paper sheet of predetermined dimensions is fed toward the first groove at the predetermined position on the outer peripheral surface of the drum substantially along a tangential line at the predetermined position in a predetermined rotational direction of the drum. A leading end portion of the printing paper sheet is pushed into the first groove by means of a first holding rod extending in the longitudinal direction of the drum. As a result, the leading end portion of the printing paper sheet is held at the predetermined position on the outer peripheral surface of the drum.
If the drum starts to rotate in the predetermined direction, a second holding rod extending in the longitudinal direction pushes the printing paper sheet on the outer peripheral surface of the drum. While the drum makes a first one rotation, the second holding rod prevents an area of the printing paper sheet, which ranges from its leading end portion to the second holding rod, from separating from the outer peripheral surface of the drum. A second groove extending along the first groove is formed at a predetermined position (on the downstream side of the first groove) on the outer peripheral surface of the drum, which is apart from the first groove in a direction opposite to the predetermined rotational direction of the drum. The second holding rod pushes a trailing end portion of the printing paper sheet into the second groove and holds it in the second groove. The combination of the second holding rod and second groove constitutes a trailing end-of-printing medium holding device.
In the printing medium winding apparatus described in the above-mentioned KOKOKU Publication No. 55-13912, a wide groove extending in the longitudinal direction of the drum is provided at a predetermined position on the outer peripheral surface of the drum. A printing paper sheet of predetermined dimensions is fed toward the wide groove at the predetermined position on the outer peripheral surface of the drum substantially along a tangential line at the predetermined position in a predetermined rotational direction of the drum. A leading end portion of the printing paper sheet is clamped on a trailing end portion of the wide groove on the outer peripheral surface of the drum in the predetermined rotational direction by means of a clamp plate which is selectively openable.
If the drum then starts to rotate in the predetermined direction, a push roller pushes the printing paper sheet on the outer peripheral surface of the drum and prevents an area of the printing paper sheet, which ranges between its leading end portion and the push roller, from separating from the outer peripheral surface of the drum while the drum makes first one rotation. In addition, an engaging hook, which can selectively project and retreat, is provided in the wide groove adjacent to a leading edge of the wide groove in the predetermined rotational direction. An engaging hole for engagement with the engaging hook is formed in a trailing end portion of the printing paper sheet. The projecting engaging hook is engaged in the engaging hole in the printing paper sheet pushed on the outer peripheral surface of the drum by means of the push roller. Thereby, the trailing end portion of the printing paper sheet is held on the outer peripheral surface of the drum. The projectable engaging hook and the engaging hole in the trailing end portion of printing paper sheet constitute a trailing end-of-printing medium holding device.
In the printing medium winding apparatus of the above-mentioned Jpn. Pat. Appln. KOKAI Publication No. 54-38813, the rotation of the drum has to be once stopped, each time the leading and trailing end portions of the printing paper sheet are held in the first and second grooves in the outer peripheral surface of the drum by using the first and second holding rods and each time the leading and trailing end portions of the printing paper sheet are separated from the first and second grooves in the outer peripheral surface of the drum. In addition, during a time period between a time when the leading end portion of the printing paper sheet is held in the first groove in the outer peripheral surface of the drum by means of the first holding rod and a time when the trailing end portion of the printing paper sheet is held in the second groove in the outer peripheral surface of the drum by means of the second holding rod, the printing paper sheet is pushed on the outer peripheral surface of the drum by the second holding rod and slid relative to the second holding rod. Consequently, a tensile force is applied to the printing paper sheet on the outer peripheral surface of the drum. The tensile force increases as the rotational speed of the drum increases. This may result in breakage of the leading end portion of the printing paper sheet or breakage of a portion of the paper sheet which is in contact with the second holding rod. Because of this, in an ink-jet printer using the printing medium winding apparatus of KOKAI Publication No. 54-38813, the number of printing paper sheets, on which information can be printed per unit time, cannot be increased.
In the printing medium winding apparatus described in the above-mentioned KOKOKU Publication No. 55-13912, only a special paper sheet having the engaging hole with predetermined dimensions at the predetermined position of the trailing end portion thereof can be used.
The present invention has been made under the above circumstances, and its object is to provide a printing medium winding apparatus capable of exactly holding a trailing end portion of an ordinary printing medium with predetermined dimensions on an outer peripheral surface of a drum at a higher speed than in the prior art, without a need to use a special printing medium, and also to provide an ink-jet printer having such a printing medium winding apparatus, thereby increasing, as compared to the prior art, the number of printing paper sheets on which information can be exactly and clearly printed per unit time.